1. Technical Field
The present disclosure relates to a workpiece conveying apparatus for conveying a plurality of electronic components, such as chip electronic components, and in particular, to a workpiece conveying apparatus and an electronic component conveying apparatus for conveying a workpiece by moving, on a conveyer stage, a conveyer table having a plurality of through-holes formed therein, each of said through-holes serving as a container portion for a workpiece.
2. Background Art
In general, in order to manufacture chip electronic components, after chip electronic components are produced and the characteristics of the chip electronic components are measured, the chip electronic components are classified into a non-defective component group and a defective component group on the basis of the characteristics. In addition, the produced chip electronic components are categorized into a plurality of groups in accordance with the characteristics. In order to automate such operations and increase the productivity of manufacturing, different manufacturing equipments have been utilized for manufacturing the chip electronic components.
For example, in Patent Document 1 listed below, an example of such an electronic component conveying apparatus is described. In order to convey an electronic component, this electronic component conveying apparatus includes a disc-shaped conveyer table disposed so as to be in contact with a conveying surface of a table base. The disc-shaped conveyer table is connected to a rotation driving source so as to rotate about the center axis thereof. A plurality of through-holes each containing an electronic component sequentially supplied from a hopper are formed in the disc-shaped conveyer table along the periphery of the conveyer table. A hopper supplies an electronic component into each of the through-holes. Since the conveyer table rotates while sliding over the conveying surface of the base table, the electronic components are conveyed in the circumferential direction of the conveyer table.
While the electronic component is being conveyed in the circumferential direction of the conveyer table, the characteristics of the electronic component are measured. Subsequently, after the characteristics of the electronic component are measured, the electronic component is picked up from the through-hole by using appropriate electronic component pick-up means so as to be classified into a non-defective component group and a defective component group or classified into groups in accordance with the characteristics.
At that time, in order to maintain the proper orientation of the electronic component when the electronic component is conveyed, the conveying surface includes a suction recess portion formed therein. The suction recess portion communicates with the through-holes. The suction recess portion is connected to, for example, a suction vacuum source.
In addition, in order to pick up the electronic component after the characteristics of the electronic component are inspected, a structure as shown in FIG. 7 is employed. That is, as shown in FIG. 7, a conveyer table 102 of an electronic component conveying apparatus 101 includes a through-hole 102a. The through-hole 102a accommodates an electronic component 104. A surface 102b, one of two surfaces of the conveyer table 102, is in contact with a conveying surface 103a of a table base 103.
An exhaust hole 103b is open in the conveying surface 103a of the table base 103 at a location at which the electronic component 104 is picked up. The exhaust hole 103b extends from the conveying surface 103a to a surface 103c opposite the conveying surface 103a. In addition, the exhaust hole 103b is connected to a compressed air supply hose 105. The compressed air supply hose 105 is connected to a compressed air supply source, such as a compressor or a compressed-air cylinder.
When the electronic component 104 arrives at a location at which the electronic component 104 is picked up by rotation of the conveyer table 102 after the electronic component 104 is measured, the exhaust hole 103b faces part of the through-hole 102a. The exhaust hole 103b has a diameter smaller than that of the opening of the through-hole 102a. Subsequently, compressed air is ejected from the exhaust hole 103b. The pressure of the compressed air moves the electronic component 104 outside the through-hole 102a. Thus, the electronic component 104 is picked up.
In this way, the electronic component 104 is picked up without being subjected to mechanical shock. Accordingly, the occurrence of damage of the electronic component 104 can be reduced.
[Patent Document 1] Japanese Unexamined Patent Application Publication No. 2004-226101
As described above, the conveyer table 102 moves while sliding over the conveying surface 103a of the table base 103 independently from the table base 103. Accordingly, after the electronic component 104 is picked up using the compressed air, the conveyer table 102 further rotates. As a result, the exhaust hole 103b is closed by the surface 102b of the conveyer table 102 again.
In this case, no problems occur if the compressed air is completely discharged into the through-hole 102a, the electronic component 104 is picked up, and subsequently, the exhaust hole 103b is closed by the surface 102b of the conveyer table 102.
However, if the conveying speed is increased, the opening of the exhaust hole 103b may be closed by the conveyer table 102 with the compressed air remaining in the exhaust hole 103b. In such a case, since the compressed air remains in the exhaust hole 103b, residual pressure occurs.
Accordingly, when the conveyer table 102 further rotates so that the next through-hole, which accommodates an electronic component that should not be picked up at the above-described electronic component pick-up location, moves onto the exhaust hole 103b, the electronic component that should not be picked up may be picked up due to the residual pressure. Therefore, in the existing electronic component conveying apparatuses, in order to discharge the air completely, the conveyer table 102 should not be rotated and moved immediately after the electronic component 104 is picked up. For this reason, the conveyer table 102 needs to be stopped for a predetermined time period. That is, a stoppage time is needed for releasing the residual pressure and, therefore, the electronic component conveying apparatuses cannot operate at high speed.
In particular, as the size of an electronic component decreases, the size of the exhaust hole 103b needs to be decreased. Accordingly, since the small-sized exhaust hole 103b cannot discharge a sufficient amount of air, a longer stoppage time is needed for releasing the residual pressure. In addition, even when the stoppage time is increased, it is still difficult to sufficiently release the residual pressure.